Abstract

The optical breakdown induced in air at atmospheric pressure by Nd:YAG Q-switched laser pulses is studied in terms of the spectral features of the emitted radiation in the wavelength range 180–850 nm during the first 200 ns after the laser pulse onset. During the plasma build up, radiation emission features intense, broadband, and structureless ultraviolet–visible spectra before the appearence of atomic lines on the microsecond scale. Also, the emitting plasma kernel, imaged during the buildup and decay stages in the early tens of nanoseconds, turns out to have a size of ∼0.3 mm and a volume of ∼0.02 mm3. The coupling of direct emission data and broadband absorption measurements allowed us to retrieve peak values of electron temperature above 100,000 K and of an optical depth of the order of unity, under the assumptions of local thermodynamic equilibrium and a homogeneous kernel. The simultaneous occurrence of such temporal, spatial, and spectral features of the plasma kernel suggests its exploitation as a pulsed, bright, and broadband ultraviolet–visible light source.

© 1998 Optical Society of America

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References

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  1. F. B. A. Früngel, High-Speed Pulse Technology (Academic, New York, 1965).
  2. S. Itami, T. Araki, “An intense, broadband emission spectrum, thyratron-gated nanosecond light source using a commercially available Xe short-arc lamp,” Rev. Sci. Instrum. 67, 3035–3038 (1996).
    [CrossRef]
  3. J. M. Meek, J. D. Craggs, eds., Electrical Breakdown of Gases (Wiley, New York, 1978).
  4. R. J. Nordstrom, “Study of laser-induced plasma emission spectra of N2, O2, and ambient air in the region 350 nm to 950 nm,” Appl. Spectrosc. 49, 1490–1499 (1995).
    [CrossRef]
  5. J. R. Hollahan, A. T. Bell, eds., Techniques and Applications of Plasma Chemistry (Wiley, New York, 1974).
  6. L. J. Radziemski, D. A. Cremers, eds., Laser-Induced Plasmas and Applications (Marcel Dekker, New York, 1989).
  7. A. Borghese, A. D’Alessio, G. Russo, C. Venitozzi, “Time resolved electrical and spectroscopic study of very short spark discharges,” in Proceedings of the International Symposium on Diagnostics and Modelling of Combustion in Reciprocating Engines (Japanese Society of Mechanical Engineers, Tokyo, Japan, 1985), pp. 77–83.
  8. H. R. Griem, ed., Plasma Spectroscopy (McGraw-Hill, 1964).
  9. R. H. Huddlestone, S. L. Leonard, eds., Plasma Diagnostic Techniques (Academic, New York, 1965).
  10. A. Borghese, S. S. Merola, “Time resolved spatial and spectral analysis of a special light source for the broadband extinction spectroscopy technique,” in Proceedings of FRANTIC ’97 (Friendly Related Appointments, National and/or Transnational and/or International Congress) (Associazione Sezione Italiana del Combustion Institute, Naples, Italy, 1997), p. IV-3.
  11. A. Borghese, S. S. Merola, “Detection of extremely fine carbonaceous particles in the exhausts of diesel and spark-ignited i.c. engines, by means of broadband extinction and scattering spectroscopy in the ultraviolet band 190 nm-400 nm,” to be presented at the Twenty-seventh International Symposium on Combustion, Boulder, Colorado, 1998 (Combustion Institute, Pittsburgh, Pa., 1998).
  12. S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

1996 (1)

S. Itami, T. Araki, “An intense, broadband emission spectrum, thyratron-gated nanosecond light source using a commercially available Xe short-arc lamp,” Rev. Sci. Instrum. 67, 3035–3038 (1996).
[CrossRef]

1995 (1)

Araki, T.

S. Itami, T. Araki, “An intense, broadband emission spectrum, thyratron-gated nanosecond light source using a commercially available Xe short-arc lamp,” Rev. Sci. Instrum. 67, 3035–3038 (1996).
[CrossRef]

Borghese, A.

A. Borghese, A. D’Alessio, G. Russo, C. Venitozzi, “Time resolved electrical and spectroscopic study of very short spark discharges,” in Proceedings of the International Symposium on Diagnostics and Modelling of Combustion in Reciprocating Engines (Japanese Society of Mechanical Engineers, Tokyo, Japan, 1985), pp. 77–83.

A. Borghese, S. S. Merola, “Time resolved spatial and spectral analysis of a special light source for the broadband extinction spectroscopy technique,” in Proceedings of FRANTIC ’97 (Friendly Related Appointments, National and/or Transnational and/or International Congress) (Associazione Sezione Italiana del Combustion Institute, Naples, Italy, 1997), p. IV-3.

A. Borghese, S. S. Merola, “Detection of extremely fine carbonaceous particles in the exhausts of diesel and spark-ignited i.c. engines, by means of broadband extinction and scattering spectroscopy in the ultraviolet band 190 nm-400 nm,” to be presented at the Twenty-seventh International Symposium on Combustion, Boulder, Colorado, 1998 (Combustion Institute, Pittsburgh, Pa., 1998).

S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

D’Alessio, A.

S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

A. Borghese, A. D’Alessio, G. Russo, C. Venitozzi, “Time resolved electrical and spectroscopic study of very short spark discharges,” in Proceedings of the International Symposium on Diagnostics and Modelling of Combustion in Reciprocating Engines (Japanese Society of Mechanical Engineers, Tokyo, Japan, 1985), pp. 77–83.

D’Anna, A.

S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

Früngel, F. B. A.

F. B. A. Früngel, High-Speed Pulse Technology (Academic, New York, 1965).

Itami, S.

S. Itami, T. Araki, “An intense, broadband emission spectrum, thyratron-gated nanosecond light source using a commercially available Xe short-arc lamp,” Rev. Sci. Instrum. 67, 3035–3038 (1996).
[CrossRef]

Kurz, M.

S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

Merola, S. S.

A. Borghese, S. S. Merola, “Detection of extremely fine carbonaceous particles in the exhausts of diesel and spark-ignited i.c. engines, by means of broadband extinction and scattering spectroscopy in the ultraviolet band 190 nm-400 nm,” to be presented at the Twenty-seventh International Symposium on Combustion, Boulder, Colorado, 1998 (Combustion Institute, Pittsburgh, Pa., 1998).

S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

A. Borghese, S. S. Merola, “Time resolved spatial and spectral analysis of a special light source for the broadband extinction spectroscopy technique,” in Proceedings of FRANTIC ’97 (Friendly Related Appointments, National and/or Transnational and/or International Congress) (Associazione Sezione Italiana del Combustion Institute, Naples, Italy, 1997), p. IV-3.

Nordstrom, R. J.

Russo, G.

A. Borghese, A. D’Alessio, G. Russo, C. Venitozzi, “Time resolved electrical and spectroscopic study of very short spark discharges,” in Proceedings of the International Symposium on Diagnostics and Modelling of Combustion in Reciprocating Engines (Japanese Society of Mechanical Engineers, Tokyo, Japan, 1985), pp. 77–83.

Venitozzi, C.

A. Borghese, A. D’Alessio, G. Russo, C. Venitozzi, “Time resolved electrical and spectroscopic study of very short spark discharges,” in Proceedings of the International Symposium on Diagnostics and Modelling of Combustion in Reciprocating Engines (Japanese Society of Mechanical Engineers, Tokyo, Japan, 1985), pp. 77–83.

Appl. Spectrosc. (1)

Rev. Sci. Instrum. (1)

S. Itami, T. Araki, “An intense, broadband emission spectrum, thyratron-gated nanosecond light source using a commercially available Xe short-arc lamp,” Rev. Sci. Instrum. 67, 3035–3038 (1996).
[CrossRef]

Other (10)

J. M. Meek, J. D. Craggs, eds., Electrical Breakdown of Gases (Wiley, New York, 1978).

F. B. A. Früngel, High-Speed Pulse Technology (Academic, New York, 1965).

J. R. Hollahan, A. T. Bell, eds., Techniques and Applications of Plasma Chemistry (Wiley, New York, 1974).

L. J. Radziemski, D. A. Cremers, eds., Laser-Induced Plasmas and Applications (Marcel Dekker, New York, 1989).

A. Borghese, A. D’Alessio, G. Russo, C. Venitozzi, “Time resolved electrical and spectroscopic study of very short spark discharges,” in Proceedings of the International Symposium on Diagnostics and Modelling of Combustion in Reciprocating Engines (Japanese Society of Mechanical Engineers, Tokyo, Japan, 1985), pp. 77–83.

H. R. Griem, ed., Plasma Spectroscopy (McGraw-Hill, 1964).

R. H. Huddlestone, S. L. Leonard, eds., Plasma Diagnostic Techniques (Academic, New York, 1965).

A. Borghese, S. S. Merola, “Time resolved spatial and spectral analysis of a special light source for the broadband extinction spectroscopy technique,” in Proceedings of FRANTIC ’97 (Friendly Related Appointments, National and/or Transnational and/or International Congress) (Associazione Sezione Italiana del Combustion Institute, Naples, Italy, 1997), p. IV-3.

A. Borghese, S. S. Merola, “Detection of extremely fine carbonaceous particles in the exhausts of diesel and spark-ignited i.c. engines, by means of broadband extinction and scattering spectroscopy in the ultraviolet band 190 nm-400 nm,” to be presented at the Twenty-seventh International Symposium on Combustion, Boulder, Colorado, 1998 (Combustion Institute, Pittsburgh, Pa., 1998).

S. S. Merola, M. Kurz, A. Borghese, A. D’Anna, A. D’Alessio, “Ultraviolet broadband light scattering by single metal-containing droplets,” Combust. Sci. Technol. (to be published).

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Figures (6)

Fig. 1
Fig. 1

PDA signal spectra of the light emitted by laser-induced breakdown dispersed by a 200 groove/mm grating at 10, 20, 40, and 80 ns after laser onset.

Fig. 2
Fig. 2

Emission spectra dispersed by a 360 groove/mm grating at 10, 20, 40, and 80 ns after laser onset and corrected by instrumental response (filled circles).

Fig. 3
Fig. 3

Normalized signal intensities as functions of time, emitted at wavelengths λ = 200, 300, 390 nm.

Fig. 4
Fig. 4

Selection of eight images of the plasma kernel recorded at time delays of (a) 4, (b) 6, (c) 8, (d) 10, (e) 12, (f) 14, (g) 16, and (h) 20 ns after laser onset. The laser beam travels from right to left (nominal focus at x = 0, y = 0).

Fig. 5
Fig. 5

Thin solid curve, emission intensity spectrum acquired at t = 10 ns; thick solid curve, intensity spectrum as evaluated from Eq. (5B); open circles, optical depth of plasma as evaluated from Eq. (5B); dashed curve, Planck function in Eq. (2) evaluated for T = 103,000 K.

Fig. 6
Fig. 6

Time behavior of plasma electron temperature (filled circles) and spectrally averaged optical depth (open circles) evaluated as in Fig. 5 (see text).

Equations (7)

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ε λ ,   x = k λ ,   x I T λ ,   x .
I T λ = 2 hc 2 / λ 5 exp hc / λ kT - 1 - 1 ,
d I λ ,   x / d x = ε λ ,   x - k λ ,   x I λ ,   x .
I λ = I T λ 1 - exp - k d - 1 ,
I λ = I λ + I c λ exp - k d .
k d = log I c λ / I λ - I λ ] ,
I T exp λ = I λ × I c λ / I λ + I c λ - I λ .

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